Disease Diffusion

Schærström, A.

Geographically, disease distribution or occurrence can be perceived either as the locations where cases are found or as the places where the necessary circumstances for causing illness are prevalent. Spatial diffusion theory distinguishes between two dimensions of a diffusion process. On the one hand, the routes may be determined by proximity – spreading to nearby places – or by hierarchical levels – spreading between places in a stepwise manner. On the other hand, the structure of diffusion appears as either expansion or relocation. The geographical context of health and disease can be conceived as epidemiological landscapes or landscapes of exposure. These are dynamic, i.e., their contents and extensions will change over time. The epidemiological transition might appear as a spatial diffusion of diseases, but is rather the outcome of changing ecological preconditions for disease and disease determinants. Increasing spatial connectivity has radically altered the routes and speed of diffusion. Global and local environmental changes alter the prospects for health. In the future, climatic change might affect the living conditions for agents and vectors involved in disease ecology. Understanding the geographical diffusion of diseases is important for predicting and containing diseases. GIS can be very useful tools for public health surveillance, simulation, analysis, and early warning.